What was found
CREW REPORTED, ON APPROACH TO LAND, LANDING GEAR WAS EXTENDED BUT LT MAIN GEAR DOWN AND LOCK LIGHT FAILED TO ILLUMINATE. LAMP PRESS TO TEST OK. GEAR WARNING HORN DID NOT SOUND FOR THROTTLE OR FLAP TEST. ALTERNATE GEAR EXTENSION WAS PERFORMED PER "GEAR WILL NOT EXTEND HYDRAULICALY CHECK LIST" (BLOWDOWN)BUT DOWN AND LOCK LIGHT STILL FAILED TO ILLUMINATE. EMERGENCY WAS DECLARED, APPROACH WAS CONTINUED, LANDING WAS UNEVENTFUL. MAINTENANCE INSPECTED AIRCRAFT, FOUND BROKEN WIRE ON DOWN/LOCK SWITCH.REMOVED AND REPLACED ACTUATOR ASSEMBLY AS A PRECAUTIONARY MEASURE.EXTENSION AND RETRACTION TEST PERFORMED, CHECKS OK. AIRCRAFT RELEASED BACK TO SERVICE.